This disclosure relates to the cutting of computer programmed shape and window profile(s) through a well bore casing whose inside diameter is three inches or larger, and more particularly, to the controlled and precise use of an abrasive-jet-fluid to cut a predefined shape or window through a well bore casing, thereby facilitating and providing access to the formation structure beyond the cemented casing.
Many wells today have a deviated bore drilled extending away from a generally vertical axis main well bore. The drilling of such a side-track is accomplished via multiple steps. After casing and cementing a well bore, historically a multi-stage milling process is employed to laterally cut a window through the casing at the general location where it is desired to start the side-track. Once the window is milled open, the drilling process may begin.
Although simple in concept, the execution is often complicated and difficult to achieve in a timely fashion. Several complicating factors are that the well bore casing is made of steel or similarly hard material as well as the casing is difficult to access down the well bore hole. Historically it is not uncommon to take 10 hours to complete the milling of the desired shape and/or window profile(s) through the casing using conventional machining processes. An improper shape or window profile(s) of the side-track hole cut through the steel casing may cause drill breakage during a horizontal or lateral drilling procedure.
A prior art method and apparatus for cutting round perforations and elongated slots in well flow conductors was offered in U.S. Pat. No. 4,134,453, which is hereby incorporated by reference as if fully set forth herein. The disclosed apparatus has jet nozzles in a jet nozzle head for discharging a fluid to cut the perforations and slots. A deficiency in this prior art method is that the length of the cuts that the disclosed jet nozzle makes into the rock formation is limited because the jet nozzle is stationary with respect to the jet nozzle head.
Another prior art method and apparatus for cutting panel shaped openings is disclosed in U.S. Pat. No. 4,479,541, which is hereby incorporated by reference as if fully set forth herein. The disclosed apparatus is a perforator having two expandable arms. Each arm having an end with a perforating jet disposed at its distal end with a cutting jet emitting a jet stream. The cutting function is disclosed as being accomplished by longitudinally oscillating, or reciprocating, the perforator. By a sequence of excursions up and down within a particular well segment, a deep slot is claimed to be formed.
The offered method is deficient in that only an upward motion along a well bore is possible due to the design of the expandable arms. Furthermore, the prior art reference does not provide guidance as how to overcome the problem of the two expandable arms being set against the well bore wall from preventing motion in a downward direction. A result of the prior art design deficiency is that sharp angles are formed between the well wall, thereby causing the jet streams emitted at the jets at the distal ends of the expandable arms to only cut small scratches into the well bore walls.
A further prior art method and apparatus for cutting slots in a well bore casing is disclosed in U.S. Pat. No. 5,445,220, which is hereby incorporated by reference as if fully set forth herein. In the disclosed apparatus a perforator is comprised of a telescopic and a double jet nozzle means for cutting slots. The perforator centered about the longitudinal axis of the well bore during the slot cutting operation.
The perforator employs a stabilizer means, which restricts the perforator, thus not allowing any rotational movement of the perforator, except to a vertical up and down motion. Additionally, the lifting means of the perforator was not shown or described.
An additional prior art method and apparatus for cutting casing and piles is disclosed in U.S. Pat. No. 5,381,631, which is hereby incorporated by reference as if fully set forth herein. The disclosed apparatus provides for a rotational movement in a substantially horizontal plane to produce a circumferential cut into the well bore casing. The apparatus drive mechanism is disposed down hole at the location near the cut target area. The prior art reference is deficient in that the apparatus requires multi-hoses to be connected from the surface to the apparatus for power and control.
There is a need, therefore, for a method and apparatus of cutting precise shape and window profile(s), which can be accomplished more quickly and less expensively. An additional need is to perforate casings, cut pilings below the ocean floor and to slot well bore casings using the unique programmed movement of a jetting-shoe.